Catheter system and method for boring through blocked vascular passages

ABSTRACT

A rotating cutting head catheter for passage through chronic total occlusions or other refractory atherosclerotic plaque from diseased arteries is disclosed. The catheter&#39;s rotating cutting head is designed to reside safely within an outer protective sheath when not in use. The outer protective sheath contains one or more helical grooves or slots, and the cutting head contains protruding blades or projections that fit into these helical grooves or slots. Application of torque to an inner catheter or wire attached to the cutting head applies spin to the cutting head, and the force of the sheath&#39;s helical grooves or slots against the cutting head&#39;s protruding blades or projections advances the cutting head outward from the protective sheath. Once extended, the cutting head may now rotate freely. The device may use a guidewire to direct the cutting head to the desired position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/108,433, filed on Apr. 23, 2008, entitled “CATHETER SYSTEM AND METHODFOR BORING THROUGH BLOCKED VASCULAR PASSAGES”, which is incorporatedherein by reference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BACKGROUND

A number of vascular diseases, such as coronary artery disease andperipheral vascular disease, are caused by the build-up of fattyatherosclerotic deposits (plaque) in the arteries. These deposits limitblood flow to the tissues that are supplied by that particular artery.Risk factors for this type of disease include advanced age, diabetes,high blood pressure, obesity, history of smoking, and high cholesterolor triglycerides.

When these deposits build up in the arteries of the heart, the problemis called coronary artery disease (CAD). When these deposits build up inthe arteries of a limb, such as a leg, the condition is calledperipheral artery disease (PAD). Symptoms of CAD—angina, heart disease,and heart attacks, are well known. Symptoms of PAD can include pain onwalking, and wounds that do not heal. If PAD is not treated, it caneventually produce critical limb ischemia (CLI), gangrene, and loss oflimb. Roughly 30% of the population over the age of 70 suffers from PAD.

When the plaque builds up to the point where an artery is totallyoccluded, the obstruction is referred to as a Chronic Total Occlusion(CTO). CTOs can confound the treatment of CAD, because the sudden lossof heart muscle can lead to sudden death. A CTO that occludes theperipheral arteries for PAD patients is also extremely serious. PADpatients that suffer from a CTO often enter a downward spiral towardsdeath. Often the CTO in a peripheral artery results in limb gangrene,which requires limb amputation to resolve. The limb amputation in turncauses other complications, and roughly half of all PAD patients diewithin two years of a limb amputation.

For both CAD and advanced PAD, prompt treatment of such blockages isthus essential. Here, less invasive angioplasty or atherectomyprocedures have many advantages. In these procedures, a catheter isinserted into the diseased artery and threaded to the blocked region.There the blockage may be either squeezed into a hopefully more openposition by pressure from an inflated catheter balloon (balloonangioplasty), the blocked region may be kept open by a stent, oralternatively a physician may use a catheter to surgically remove theplaque from the inside of the artery (atherectomy).

As an example, for the treatment of PAD, atherectomy devices such as theFox Hollow (now ev3) SilverHawk™ catheter (U.S. Pat. No. 6,027,514), areoften used. These catheters may be threaded (usually with the aid of aguidewire) up the artery to a blocked region. There, the physician willusually position the catheter to make multiple passes through theblocked region of the artery, each time shaving a way a ribbon ofplaque. The shaved ribbons of plaque are stored in the hollow nose ofthe device. By making multiple passes, the plaque may be substantiallyreduced, blood circulation may be restored to the limb, and the limb inturn saved from amputation.

In order to effectively treat the plaque, however, most modern cathetersneed to be threaded past the blocked region of the artery. This isbecause the active portions of most catheters, which are used to treatthe blockage, are usually located on the side of the catheter, ratherthan on the tip of the catheter. This is due to simple mechanicalnecessity. The tip of the catheter must have a very small surface area,and thus is able to treat only a very small portion of the diseasedartery. By contrast, the side of the catheter has a much larger surfacearea, and the catheter side thus conforms nicely to the sides of thediseased artery. Thus stents, balloons, atherectomy cutting tools, etc.,are usually mounted on the sides of the catheter. The catheter must bethreaded past the blocked portion of the artery in order to functionproperly.

When the artery is only partially blocked by plaque, the catheter canusually be maneuvered past the obstruction, and the active portions ofthe catheter can thus be brought into contact with the diseased portionof the artery. However when the artery is totally blocked, as is thecase with a CTO, this option is no longer possible. The tip of thecatheter encounters the obstruction, and further forward motion isblocked.

Simply trying to force a typical catheter past the obstruction usuallyisn't possible. The obstructions are typically composed of relativelytough fibrous material, which often also includes hard calcium depositsas well. Often, when physicians attempt to force guidewires or catheterspast such obstructions, the guidewire or catheter device may insteadexit the artery and enter the lumen outside the artery. This furtherdamages the artery, further complicates the procedure, and decreases thechance of success. As previously discussed, the consequences of suchprocedure failures have a high mortality rate. Thus improved methods toallow catheters and guidewires to more readily penetrate throughhardened plaque and CTO are thus of high medical importance.

A good summary of the present state of the art may be found in anarticle by Aziz and Ramsdale, “Chronic total occlusions—a stiffchallenge requiring a major breakthrough: is there light at the end ofthe tunnel?” Heart 2005; 91; 42-48.

Previous attempts to produce devices for cutting through hardened plaqueinclude U.S. Pat. Nos. 5,556,405 to Lary, 6,152,938 to Curry, and6,730,063 to Delaney et. al.

U.S. Pat. No. 5,556,405 teaches an incisor catheter which features abladed head stored in a catheter housing, which contains a number ofslits though which the blades protrude. The blade is activated by apush-pull catheter. When the push-pull catheter is pushed, the bladedhead protrudes through the slits in the housing, and the blade thuscomes into contact with hardened plaque material. The blade does notrotate, but rather delivers linear cuts.

U.S. Pat. No. 6,152,938 teaches a general purpose catheter drillingdevice for opening a wide variety of different blocked (occluded) tubes.The device anchors the tip of the drill head against a face of theocclusion, and partially rotates the drill head using a rein attached tothe drill head so that the drill head faces at an angle.

U.S. Pat. No. 6,730,063 teaches a catheter device for chemicallytreating calcified vascular occlusions. The device is a fluid deliverycatheter that delivers acidic solutions and other fluids to calcifiedplaque with the objective of chemically dissolving the calcifiedmaterial.

Several catheter devices for traversing CTO obstructions are presentlymarketed by Cordis Corporation, FlowCardia Technology, Kensey NashCorporation, and other companies. Cordis Corporation, a Johnson andJohnson Company, produces the Frontrunner® XP CTO catheter (formerlyproduced by LuMend Corporation). This catheter, discussed in U.S. Pat.No. 6,800,085 and other patents, has a front “jaw” that opens and closesas it traverses the catheter. The jaw itself does not cut, but ratherattempts to pry open the CTO as the catheter passes.

Other catheter devices use various forms of directed energy to traverseCTOs. For example, FlowCardia Technology, Sunnyvale Calif., produces theCrosser system, taught in U.S. Pat. No. 7,297,131 and other patents.This system uses an ultrasonic transducer to deliver energy to anon-cutting catheter head. This catheter head itself has a relativelysmall diameter and does not have any blades. Rather, the head, throughrapid (ultrasonic) vibration is able to push its way through a varietyof different occlusions.

Kensey Nash Corporation, Exton Pa. (formerly Intraluminal Therapeutics,Inc.), produces the Safe-Cross CTO system. This system, taught in U.S.Pat. Nos. 6,852,109 and 7,288,087, uses radiofrequency (RF) energy. Thecatheter itself is also directed in its movement by an optical(near-infrared light) sensor which can sense when the tip of thecatheter is near the wall of the artery. The optical sensor tells theoperator how to steer the catheter, and the RF ablation unit helps theoperator ablate material and cross occluded regions.

Although ingenious, the success rates with these devices still leavemuch to be desired. According to Aziz, the best reported success ratesof overcoming CTOs with prior art devices range from 56% to 75%. Azizfurther teaches that the average success rates are only in the 50-60%range. Given the huge negative impact that unsuccessfully cleared CTO'shave on patient morbidity and mortality, clearly further improvement isdesirable. An additional problem with these prior art CTO clearingdevices is that simply cutting a small channel though the CTO may not besufficient to totally resolve the medical problem. Occasionally, thedevice that traverses the CTO should also remove (debulk) a substantialportion of the occlusion. This is because as previously discussed,removal of a substantial portion of the occlusion may be required inorder to allow catheters with side mounted stents, balloons, andatherectomy cutting tools to get access to the damaged portions of theartery and make more lasting repairs. Thus improved CTO “unclogging”devices that can do the more substantial amount of CTO debulkingrequired to allow other types of catheters to pass are also desirable.

Thus there remains a need for devices that can effectively traverse CTOsand remove more substantial amounts of hardened or calcified plaque.Such devices would enable stents and other devices, such as SilverHawkatherectomy catheters, balloon catheters, etc. to be more successfullyused in high occlusion situations. This in turn should lead to improvedpatient outcomes and a reduction in patient morbidity and mortality.

SUMMARY OF THE DISCLOSURE

The present invention teaches a novel rotating cutting head catheter forcreating a passage through refractory material, such as chronic totalocclusions, refractory atherosclerotic plaque, gallstones, kidneystones, etc. from diseased arteries, veins, or other body lumens. Thecatheter's rotating cutting head is designed to reside safely within anouter protective sheath head when not in use, and this sheath head ismounted on the distal end of the catheter.

The outer protective sheath head contains one or more helical grooves orslots, and the cutting head contains protruding blades or projectionsthat fit into these helical grooves or slots. Application of torque toan inner torque communicating connector (a catheter or wire or coil, orany torque communicating mechanism attached to the cutting head) appliesspin to the cutting head, and the force of the sheath head's helicalgrooves against the cutting head's protruding blades or projectionsadvances the cutting head outward from the protective sheath. Onceextended, the cutting head may now rotate freely. In some embodiments,the center of the catheter and even the cutting head itself may behollow, and the device may use a guidewire to direct the catheter andthe cutting head to the desired position. Alternatively the guidewiremay be attached to a guide that is attached to the outside of thecatheter tube. In at least some embodiments, this sheath head acts asmotion stop, and may contain one or more motion stop elements (such as amechanical barrier) designed to restrict the forward extension of thecutting head.

Depending upon the angle and nature of the cutting head's protrudingblades, the blades may either be designed to simply cut thorough theoccluding material, without actually dislodging the occluding materialfrom the body lumen, or alternatively the blades may be designed to bothcut through the occluding material, and sever its link to the bodylumen, thereby dislodging the occluding material from the body lumen. Inthis case, the cutting head can act to actually remove (debulk) asubstantial portion of the occlusion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overview of the catheter device including the handle,the catheter, and the catheter head.

FIG. 2 shows the exterior of the catheter head with the cutting headextended out from the sheath head.

FIG. 3 shows a drawing of the catheter head (mounted on a guidewire)with the cutting head extended and cutting into a CTO plaque in anoccluded artery.

FIG. 4 shows a diagram of the cutting head unscrewing from protectiveshroud of the catheter head's sheath head.

FIG. 5 shows a close up of the catheter head showing the cutting headscrewed into a stored position inside the catheter head's protectivesheath head.

FIG. 6 shows a close up of a cutting head with an alternate protrudingblade design.

DETAILED DESCRIPTION

Although, throughout this discussion, applications of this device forcreating a passage through refractory atherosclerotic plaque fromarteries, particularly coronary or peripheral limb arteries, arefrequently used as examples, it should be understood that theseparticular examples are not intended to be limiting. Other applicationsfor the present technology may include removal of kidney stones, inwhich case the device will be intended to traverse the ureters;gallstones, in which case the device will be intended to traverse thebile duct; enlarged prostate blockage of the urethra, in which case thedevice will be intended to traverse the urethra; blocked fallopiantubes, in which case the device will be intended to traverse thefallopian tubes; treatment of blood clots, removal of material trappedin the lungs, etc. In general, any unwanted material occupying space ina body lumen may be surgically removed by these techniques. Similarly,although use in human patients is cited in most examples, it should beevident that the same techniques may be useful in animals as well.

Helical drill bits and self-tapping screw bits are widely known to behighly effective at penetrating through materials as soft as wax and asrefractory as rock and metal, and indeed such devices are widely usedfor such purposes. Although effective, drill bits are typicallyconsidered to be both powerful and extremely crude. As anyone who hasever attempted to use an electric drill can attest, drill devices,although admittedly effective at removing material, would seem to betotally unsuited for delicate vascular surgery, particularly at siteshidden deep within the body. Helical self-tapping screw bits aredesigned slightly differently. Although just as effective at cuttingthrough various materials, drill bits are configured to both cut andthen remove the material, while self-tapping screw bits are designedprimarily for cutting a passage through the material. For either type ofdevice, the problem is not the efficacy of cutting or occlusion removal;the problem is one of preventing inadvertent damage to the surroundingartery.

Surprisingly however, the present invention teaches that if theprejudice against such crude and powerful methods is overcome, andsuitable protection and control devices are devised to control the crudeand apparently overwhelming power of such “drill bit” devices, catheter“drill bit” devices suitable for delicate vascular surgery, which areboth powerful at cutting or removing occlusions, yet specific enough toavoid unwanted damage to artery walls, may be produced.

Thus, in a first aspect of the present invention, the superior materialcutting/removing properties of a “drill bit” like material removaldevice (or self-threading helical screw bit) are combined with suitableprotection and catheter guidance mechanisms which allow such powerfulcutting devices to be safely and effectively used within the confines ofdelicate arteries and other body lumens.

To do this, precise control must be exerted over the cutting edge of the“drill bit”. The bit or “cutting head” should normally be sheathed orshielded from contact with artery walls, so that inadvertent damage toartery walls can be avoided while the head of the catheter is beingthreaded to the artery to the occluded region. Once at the occlusion,the cutting portion of the cutting head (bit) should be selectivelyexposed only to the minimal extent needed to perform the relevantocclusion cutting activity. The rotation direction of the cutting headmay optionally be varied, for example by rotating the headcounter-clockwise to produce a blunt dissection through the obstacle orocclusion, and then clockwise while pulling back on the entire assembly.Once the desired cuts are made, the cutting head should then be quicklyreturned to its protective sheath. The entire device should operatewithin the millimeter diameters of a typical artery, and should becapable of being threaded on a catheter for a considerable distance intothe body.

Suitable techniques to achieve these objectives are taught in thefollowing figures and examples.

FIG. 1 shows an overview of the catheter device (100) including thecatheter body (102), the catheter handle (104), and the catheter head(106). The catheter body and catheter head, and often even the cuttinghead, are often hollow and are capable of accommodating a guidewire (notshown). A magnified view of the catheter head, showing the rotatingcutting head in an extended configuration (108), extended outside of thesheath portion of the catheter head (here this sheath is called the“sheath head”) (106) is also shown.

FIG. 2 shows the exterior of the sheath head portion of the catheterhead (106) with the cutting head (108) extended. This cutting head willnormally have one or more projecting side blades or with cutting edges(202), and additionally will often have cutting edges on the front (204)as well. The center of sheath head portion of the catheter head (106)and catheter (102) may be hollow to accommodate a guidewire. In someembodiments, the guidewire will exit the sheath portion of the catheterhead (106) on the side of catheter head (106) prior to cutting head(108) by a side opening (not shown). In other embodiments, cutting head(108) will itself be hollow and the guidewire will exit the end ofcutting head (108) through opening (206).

In the closed configuration, the rotating cutting head (108) isretracted inside the sheath head portion of catheter head (106) and thecutting edges or projections (202) from the cutting head (108) fit intohelical slots or grooves (208). This sheathed configuration preventsprojecting side cutting edges (202) and front cutting edges (204) fromaccidentally contacting the walls of the artery.

FIG. 3 shows a drawing of the catheter head (106) (with the cutting headextended from the sheath head) cutting into a CTO (304) in an occludedartery (306). In this example, the catheter and catheter head aremounted on and guided by a guidewire (302), however this will not alwaysbe the case.

As should be clear, the cutting edge of the “drill bit/screw-thread”like cutting head can easily damage artery lining (306). In order toavoid such accidental damage, precise control over the extent of cuttinghead exposure is needed. Methods to achieve such precise control areshown in FIG. 4.

FIG. 4 shows some of the details of how the cutting head (108) isunscrewed from the helical slots or grooves (208) of the sheath headportion of catheter head (106), thus exposing cutting edges (202) and(204). In (402), the cutting head (108) is shown fully exposed. Thecutting head has become fully unscrewed from helical slots (208) and isfully extended. An optional projecting post or guide (404) mounted oncutting head (108) may act to guide the rotating cutting head into andout of the helical screw-like slots (208). The coupling (406) thatcouples cutting head (108) with a torque transmitting (torquecommunicating connector) inner catheter tube or cable (408) is in theextreme distal position inside of the sheath head portion of catheterhead (106).

In (410), the cutting head is shown in its fully retracted position.Normally the cutting head will be stored in this fully retractedposition so that it can be introduced into the artery via a guidewire,and be directed to the occlusion or plaque region, without damagingnon-target regions of the artery. Note that the coupling (406) is in thefully distal position in the sheath head portion of catheter head (106),and that the protruding cutting blades (202) of cutting head (108) arefully screwed into helical screw slots (208).

In some situations, a guidewire [FIG. 3 (302)] leading to theobstruction will already have been introduced. In fact, a previousattempt to perform atherectomy may have already been made, and thisattempt may have been frustrated by refractory plaque, such as a plaquecovered with hard calcium deposits, whereupon the physician may make adecision to use the present cutting device to punch through thisrefractory plaque.

In use, the catheter head (106) and catheter tube (102) are attached tothe guidewire and are then introduced into the artery via an appropriateincision. The catheter handle (104) will remain outside of the body. Thelocation of the obstruction will generally be known, and in fact theobstruction may be imaged by fluoroscopy or other technique. Catheterhead (106) is brought up against the obstruction, and the operator willthen apply torque, often via a device mounted on catheter handle (104).This torque is usually transmitted to the catheter head (106) via aninner torque conducting catheter or wire (408), here termed a “torquecommunicating connector”. Usually outer catheter (102) will not conducttorque. Outer catheter (102) remains approximately stationary (i.e. doesnot rotate) and similarly the sheath head portion of catheter head (106)and the helical screw slots or grooves (208) also do not rotate.

The torque is communicated via coupling (406) to cutting head (108).This torque essentially causes cutting head (108) to “unscrew” from itsretracted position in the sheath head portion of catheter head (106) viathe action of the protruding blade edges (202) against helical slots orgrooves (208). This “unscrewing” circular motion is shown by the curvedarrow (412). As cutting head (108) unscrews, it starts to advance andprotrude outside of the protective sheath head shroud.

In (420), the cutting head (108) is now shown in a partially unscrewedor partially extended position. Note that the protruding blade edges(202) have moved relative to the helical sheath head screw slots orgrooves (208). Thus the blade edges (202) are now partially unscrewedfrom the helical screw slots (208) and are partially exposed. Cuttinghead (108) now is protruding out from the sheath head portion ofcatheter head casing or shroud (106), and the coupling (406) has movedpartially toward the distal end of the catheter.

It should be evident that by reversing the direction of the torque, thecutting head may be again retracted into the sheath head when this isdesired. The catheter can be repositioned for another cut, and theprocess of cutting head extension, cutting, and retraction can berepeated as many times as necessary.

Thus the present invention controls the aggressive cutting power of the“drill bit” cutting head by exposing only as much of the cutting head ata time as needed for the task at hand.

FIG. 5 shows a close up of the sheath head portion of the catheter headshowing the cutting head screwed into a stored position inside theprotective sheath head shroud. This angle allows the helical screw slotsor grooves (208) to be easily seen, and cutting head (108) can also beseen inside of the sheath head portion of catheter head (106).

FIG. 6 shows a close up of an alternate design cutting head (108) withspiral shaped protruding cutting edges (202).

The sheath head portion of catheter head (106) will normally be betweenabout 1 to 2.2 millimeters in diameter, and the catheter body (102) willtypically also have a diameter of approximately 1 to 3 millimeters (3-9French), and a length between 50 and 200 cm. The sheath head may be madefrom various materials such as hard plastics, metals, or compositematerials. Examples of such materials include NiTi steel,platinum/iridium or stainless steel.

Although sheath head (106) contains slots or grooves designed to impartforward motion to cutting head (108) when cutting head is rotated, andalthough these slots or grooves are referred to as “helical” grooves orslots, due to the short length of the sheath head and overall catheterhead, the slots or grooves do not have to be in the exact mathematicalshape of a helix. In fact a variety of shapes that differ somewhat froma mathematically pure helix configuration will suffice. In general, theslot or groove must be such that torque applied to the cutting headcauses the cutting head to both rotate and advance, and any such slot orgroove is here designated as a “helical” slot or groove. Also, for thisdiscussion, a “slot” is considered to be an opening that extends fromthe inside to the outside of the hollow catheter head (106), while a“groove” is similar to a rifle groove in that a “groove” does not extendall the way from the inside of the hollow sheath head to the outside,but rather only penetrates partway through the sheath head material.

The cutting head (108) will often be made of materials such as steel,carbide, or ceramic. The blades of the cutting head (202), (204) canoptionally be hardened by coating with tungsten carbide, ME-92, etc.Materials suitable for this purpose are taught in U.S. Pat. Nos.4,771,774; 5,312,425; and 5,674,232. The angle of the blades and thedetails of their design will differ depending upon if the head isintended to simply cut through the occluding material, of if it isintended to cut through and actually remove (debulk) portions of theocclusion. For example, blades intended for to remove material may curveat an angle such that they will tend to sever the link between theoccluding material and the body lumen, while blades intended just forcutting will have an alternate angle that tends not to sever this link.

In some embodiments, the catheter may be composed of two differenttubes. In this configuration, there may be an outer catheter tube (102),which will often be composed of a flexible biocompatible material. Theremay also be an inner tube (408) chosen for its ability to transmittorque from the catheter handle (104) to the cutting head (108) (viacoupling (406)). The inner torque transmitting tube (which is onepossible type of “torque communicating connector”) is able to twistrelative to the outer catheter tube so that when torque is applied tothe inner tube at the handle end (104), the cutting head (108) willrotate, but the catheter sheath head itself, which is connected to theouter catheter tube, will remain roughly stationary. Alternatively acable may be used in place of inner tube (408).

The outer catheter body (102) may often be made from organic polymermaterials extruded for this purpose, such as polyester,polytetrafluoroethylene (PTFE), polyurethane, polyvinylchloride, siliconrubber, and the like. The inner torque conducting catheter (408) may becomposed of these materials or alternatively may be composed from metalcoils, wires, or filaments.

In many embodiments, the catheter will be designed to be compatible witha monorail guidewire that has a diameter of about 0.014″, or between0.010″ and 0.032″. For example, the outer catheter jacket may containattached external guides for the monorail guidewire. In this case, theguidewire may exit these external guides either prior to the catheterhead, or midway through the catheter head. Alternatively, the cathetermay be hollow, and be located over the guidewire for the entire lengthof the catheter.

The catheter handle (104) will normally attach to both outer cathetertube (102), and inner tube or cable (408). Usually handle (104) willcontain at least a knob, dial, or lever that allows the operator toapply torque to the inner torque transmitting tube or cable (408). Insome embodiments, sensors may be used to determine how much the cuttinghead (108) has rotated or extended relative to the sheath head portionof catheter head (106), and these sensors, possibly aided by amechanical or electronic computation and display mechanism, may show theoperator how much the cutting head has rotated and or extended.

In some embodiments, the catheter handle (104) will be designed withknobs or levers coupled to mechanical mechanisms (such as gears, torquecommunicating bands, etc.) that manually rotate and advance/retract thecatheter tip, and the operator will manually control the tip with gentleslow rotation or movement of these knobs or levers. In other embodimentsthe catheter handle will contain a mechanism, such as an electronicmotor, and a control means, such as a button or trigger, that will allowthe user to rotate and advance the cutting head in a precise andcontrolled manner. This mechanism may, for example, consist of amicroprocessor or feedback controlled motor, microprocessor, andsoftware that may act to receive information from a cutting headrotation or extension sensor, and use this rotation feedback data, inconjunction with operator instructions delivered by the button ortrigger, to advance or retract the cutting head by a precise amount foreach operator command. This way the operator need not worry about anyerrors induced by the spring action of the inner torque transmittingtube or cable (408). The microprocessor (or other circuit) controlledmotor can automatically compensate for these errors, translate button ortrigger presses into the correct amount of torque, and implement thecommand without requiring further operator effort. Alternativelynon-microprocessor methods, such as a vernier or a series of guidedmarkings, etc., may be used to allow the operator to compensate fordifferences in the rotation of the torque communicating connector andthe rotation of the cutting head, or for the extent that which saidcutting head exits said hollow sheath head.

In some embodiments, the catheter head may be equipped with additionalsensors, such as ultrasonic sensors to detect calcified material,optical (near infrared) sensors to detect occlusions or artery walls, orother medically relevant sensors. If these sensors are employed, in somecases it may be convenient to locate the driving mechanisms for thesesensors in the catheter handle (104) as well.

Additional means to improve the efficacy of the cutting head may also beemployed. Thus the cutting head may be configured to vibrate at high(ultrasonic) frequency, perform radiofrequency (RF) tissue ablation,generate localized areas of intense heat, conduct cutting light (e.g.laser or excimer laser), or other directed energy means.

The cutting head may be composed of alternative designs and materials,and these designs and materials may be selected to pick the particularproblem at hand. As an example, a cutting head appropriate for useagainst a calcified obstruction may differ from the cutting headappropriate for use against a non-calcified obstruction. Similarly thecutting head appropriate for use against a highly fibrous obstructionmay be less appropriate against a less fibrous and fattier obstruction.The length or size of the obstruction may also influence head design.

Although multiple catheters, each composed of a different type ofcutting head, may be one way to handle this type of problem, in othercases, a kit composed of a single catheter and multiple cutting heads(108) and optionally multiple sheath heads (106) may be more costeffective. In this type of situation, the cutting heads (108) may bedesigned to be easily mounted and dismounted from coupling (406). Aphysician could view the obstruction by fluoroscopy or other technique,and chose to mount the cutting head design (and associated sheath headdesign) best suited for the problem at hand. Alternatively, if theblades (202), (204) on cutting head (108) have become dull or chippedfrom use during a procedure, a physician may chose to replace dull orchipped cutting head (108) with a fresh cutting head, while continuingto use the rest of the catheter.

For some applications, it may also be useful to supply variousvisualization dyes or therapeutic agents to the obstruction using thecatheter. Here, the dye or therapeutic agent may be applied by eithersending this dye up to the catheter head through the space between theexterior catheter (102) and the interior torque catheter (408), oralternatively if torque catheter (408) is hollow, through the interiorof torque catheter (408). If cutting head (108) also has a hollowopening (206), then the dye or therapeutic agent may be applied directlyto time obstruction, even while cutting head (108) is cutting throughthe obstruction.

Examples of useful dyes and therapeutic agents to apply includefluoroscopic, ultrasonic, MRI, fluorescent, or luminescent tracking andvisualization dyes, anticoagulants (e.g. heparin, low molecular weightheparin), thrombin inhibitors, anti-platelet agents (e.g. cyclooxygenaseinhibitors, ADP receptor inhibitors, phosphodiesterase inhibitors,Glycoprotein inhibitors, adenosine reuptake inhibitors),anti-thromboplastin agents, anti-clot agents such as thrombolytics (e.g.tissue plasminogen activator, urokinase, streptokinase), lipases,monoclonal antibodies, and the like.

In some embodiments, it may be useful to construct the cutting head outof a material that has a radiopaque signature (different appearanceunder X-rays) that differs from the material used to construct thehollow sheath head portion of the catheter head. This will allow thephysician to directly visualize, by fluoroscopic or other x-ray imagingtechnique, exactly how far the cutting head has advanced outside of thecatheter sheath head.

1. A method of delivering a guidewire across an atheroscleroticocclusion or lesion in a vascular lumen while protecting the vascularlumen, said method comprising: passing a distal end of a catheter tubehaving a rotatable cutting head and a sheath through the vascular lumento the occlusion or lesion, wherein the rotatable cutting head isretracted within the sheath during the passing step such that one ormore helical cutting surfaces extending proximally along the rotatablecutting head are engaged with one or more helical slots extendinglaterally through a sidewall of the sheath; extending the rotatablecutting head from the sheath such that the one or more helical cuttingsurfaces extend at least partially out of the sheath; rotating therotatable cutting head; advancing said rotating cutting head across saidocclusion or lesion to pass through occluding material without removingthe occluding material; and passing a guidewire through a guidewirepassageway extending through the catheter tube after the distal end ofthe catheter tube has passed beyond the atherosclerotic occlusion sothat the guidewire spans the atherosclerotic occlusion or lesion.
 2. Themethod of claim 1, wherein the rotatable cutting head is rotated byrotation of a drive shaft extending the length of the catheter.
 3. Themethod of claim 1, further comprising varying the direction of rotationof the rotatable cutting head as it is advanced across the occlusion orlesion.
 4. The method of claim 1, further comprising alternatelyrotating the rotatable cutting head clockwise and counterclockwise asthe rotating cutting head is advanced across the occlusion or lesion. 5.The method of claim 1, further comprising dispensing a therapeutic agentor visualization dye agent through the catheter tube.
 6. The method ofclaim 1, wherein the advancing step comprises cutting the occlusion orlesion with the one or more helical cutting surfaces on said rotatablecutting head.
 7. The method of claim 1, further comprising applyingultrasonic vibration, radiofrequency (RF) energy, or light energy to thecutting head, occlusion, or lesion.
 8. The method of claim 1, furthercomprising using the guidewire spanning the atherosclerotic occlusion orlesion to treat the occlusion or lesion by atherectomy, stenting, orballoon angioplasty during the same procedure.
 9. The method of claim 1,further comprising imaging the vascular lumen as the rotatable cuttinghead is advanced.
 10. A method of delivering a guidewire across anatherosclerotic occlusion or lesion in a vascular lumen while protectingthe vascular lumen, said method comprising: passing a distal end of acatheter tube having a rotatable cutting head and a sheath through thevascular lumen to the occlusion or lesion, wherein the rotatable cuttinghead is retracted within the sheath during the passing step such thatone or more helical cutting surfaces extending proximally along therotatable cutting head are engaged with one or more helical slotsextending laterally through a sidewall of the sheath; extending therotatable cutting head from the sheath such that the one or more helicalcutting surfaces extend at least partially out of the sheath; rotatingthe rotatable cutting head alternately clockwise and counterclockwise;advancing said rotating cutting head across said occlusion or lesion topass through occluding material without removing the occluding material;imaging the vascular lumen as the rotatable cutting head is advanced;and passing a guidewire through a guidewire passageway extending throughthe catheter tube after the distal end of the catheter tube has passedbeyond the atherosclerotic occlusion so that the guidewire spans theatherosclerotic occlusion or lesion.
 11. A method of delivering aguidewire across an atherosclerotic occlusion or lesion in a vascularlumen while protecting the vascular lumen, said method comprising:passing a distal end of a catheter tube having a rotatable cutting headand a sheath through the vascular lumen to the occlusion or lesion,wherein the rotatable cutting head is retracted within the sheath duringthe passing step such that one or more helical cutting surfacesextending proximally along the rotatable cutting head are engaged withone or more helical slots extending laterally through a sidewall of thesheath to shield the one or more helical cutting surfaces from contactwith the vascular lumen; extending the rotatable cutting head from thesheath such that the one or more helical cutting surfaces extend atleast partially out of the sheath; rotating the rotatable cutting head;advancing said rotating cutting head across said occlusion or lesion topass through occluding material without removing the occluding material;and passing a guidewire through a guidewire passageway extending throughthe catheter tube after the distal end of the catheter tube has passedbeyond the atherosclerotic occlusion so that the guidewire spans theatherosclerotic occlusion or lesion.
 12. The method of claim 11, whereinthe rotatable cutting head is rotate by rotation of a drive shaftextending the length of the catheter.
 13. The method of claim 11,further comprising varying the direction of rotation of the rotatablecutting head as it is advanced across the occlusion or lesion.
 14. Themethod of claim 11, further comprising dispensing a therapeutic agent orvisualization dye agent through the catheter tube.
 15. The method ofclaim 11, further comprising applying ultrasonic vibration,radiofrequency (RF) energy, or light energy to the cutting head,occlusion, or lesion.
 16. The method of claim 11, further comprisingusing the guidewire spanning the atherosclerotic occlusion or lesion totreat the occlusion or lesion by atherectomy, stenting, or balloonangioplasty during the same procedure.
 17. The method of claim 11,further comprising imaging the vascular lumen as the rotatable cuttinghead is advanced.